Transparent spherical domes mounted on a base do not require dynamic seals, but require very precise mechanical centration of interior gimbal mechanisms, are expensive and often fragile, or exhibit high optical scattering. Spring loaded rotary Teflon seals are in common use, but rotational friction is often higher than desired, the seal often has greater leakage than desirable when the gimbal mechanism is not rotating, and seal replacement is needed more often than desirable.
Conventional spring-energized, dynamic (rotary joint), rotational Teflon seals often compromise between friction of adjacent elements of the seal and the inward leak rate of water vapor or water around the seal. The negative result is generally that the leak rate around the rotational seal is high enough to require frequent maintenance action, such as gas purging and desiccant replacement and, at the same time, there is much higher friction between the dome and the base upon which it rotates than is desirable. In some infrared and electro-optic systems, the rotary motion between a dome and its base is only required for a relatively short period that is defined by the external cueing and/or test signals.
A need therefore exists in the art for a dynamic rotational seal that has a rotational friction that is much lower than found in the prior art, and has improved environmental sealing against air, moisture and other contaminants external to the dome or a rotary sealed turret in cued or operation upon command pointing and tracking systems. In addition, a need exists in the art for a dynamic rotational seal that requires much less maintenance than prior art seals.